Expendable work support for a burning table

ABSTRACT

The combination of a table for cutting steel plate and an exhaust system for evacuating the fumes and smoke produced by the cutting operation. The expendable grating of the cutting table utilizes bars which are diagonal to the usual cutting directions and are connected by staggered stiffening bars also diagonally located so that the bars are not normally cut along their longitudinal axis. Duct work under the grating comprises heavy vertically extending removable plates resting on edge which additionally provide support for the grating and lead to an elongated exhaust manifold channel having a plurality of openings and a normally closed plate covering each of such openings. The openings are disposed in a horizontal dividing plate and commu nicate with the space formed between each of the vertically extending plates making up the ductwork under the grating. The cover plates are hinged and raised from a horizontal position by a pneumatic cylinder actuated through a photoelectric cell which is responsive to light from plasma of the cutting torch. The photoelectric cell further actuates adjacent cover plates on either side of the cover plate which corresponds to the duct with which the photoelectric cell involved is aligned. Each hinged cover plate has a deep lip soft sealed ring which seats on the peripheral surface of the dividing plate about the corresponding opening and the arrangement is such that the fumes must make a 90* turn prior to entering the opening which slings out heavy particles which then drop to the bottom of the exhaust chamber for easy removal.

States Walters et al.

atent 1 EXPENIDABLE WORK SUPPORT F OR A BURNING TABLE [75] Inventors:Joseph J. Walters; Verdun R.

McGibbon, both of Coatesville, Pa.

[73] Assignee: Lukens Steel Company, Coatesville,

[22] Filed: June 8, 1972 [21] App]. No.: 260,753

Related US. Application Data [62] Division of Ser. No. 88,876, Nov. 12,1970, Pat. No.

[52] US. Cl 266/1 R [51] Int. Cl B23k 7/02 [58] Field of Search 148/9 R,9 C, 9.5;

266/23 R, 23 B, 23 E, 23 H, 23 HH, 23 K, 23 M, 23 Q; 269/289, 296;432/70, 71, 74

[56] References Cited UNITED STATES PATENTS 3,436,067 4/1969 Dodge et al266/23 K Primary Examiner--Gerald A. Dost Att0rneyMason, Mason &Albright [57] ABSTRACT The combination of a table for cutting steelplate and an exhaust system for evacuating the fumes and smoke producedby the cutting operation. The expendable grating of the cutting tableutilizes bars which are diagonal to the usual cutting directions and areconnected by staggered stiffening bars also diagonally located so thatthe bars are not normally cut along their longitudinal axis. Duct workunder the grating comprises heavy vertically extending removable platesresting on edge which additionally provide support for the grating andlead to an elongated exhaust manifold channel having a plurality ofopenings and a normally closed plate covering each of such openings. Theopenings are disposed in a horizontal dividing plate aaaeaanunaare wasthe space formed between each of the vertically extending plates makingup the ductwork under the grating. The cover plates are hinged andraised from a horizontal position by a pneumatic cylinder actuatedthrough a photoelectric cell which is responsive to light from plasma ofthe cutting torch. The photoelectric cell further actuates adjacentcover plates on either side of the cover plate which corresponds to theduct with which the photoelectric cell involved is aligned. Each hingedcover plate has a deep lip soft sealed ring which seats on theperipheral surface of the dividing plate about the corresponding openingand the arrangement is such that the fumes must make a 90 turn prior toentering the opening which slings outheavy particles which then drop tothe bottom of the exhaust chamber for easy removal.

14 Claims, -7 Drawing Figures PATENIEB JAN 8 I974 SHEET 2 OF 4 PATENIED8W 3,784,176

SHEU [1F 4 AIR Emzssuma FLOW CONTROL VALVE WITH BUILT IN CHECK VALVEEXPENDABLE WORK SUPPORT FOR A BURNING TABLE RELATED APPLICATIONS This isa divisional application of application Ser. No. 88,876 filed Nov. 12,1970, and now U.S. Pat. No. 3,701,514.

BACKGROUND OF THE INVENTION The invention involves a cutting table withan expendable grating in combination with an exhaust system wherein theexhaust action is largely localized to the area where fumes and smokeare produced by the cutting torch.

Heretofore, buildings at steel plants and the like which were utilizedfor cutting steel and alloy plate were heavily contaminated with smokeand fumes caused by the cutting operation. Due to the contamination, itwas not unusual for vision to be so restricted within the building thatone could not see from one side to the other. It was necessary for theoperator of the torch to utilize special breathing apparatus and the jobwas a dirty and unpopular one. A substantial portion of the contaminatesproduced by the plasma torch resulted not only from the plate being cutby the torch but also from the underlying structure which supported theplate and which, of necessity, was cut at least in its upper aspects atthe same time. The problem of exhausting a cutting table for steel plateis aggravated because it must be sufficiently clear above same to permitloading and unloading of steel plate by means of the gantry or boomarrangement. Cutting tables are of a necessity large, for example theymay cover an area in excess of l8 by 36 feet. To provide an overheadexhaust system for an area this size would require not only a very highcapacity exhaust fan or other exhausting means but also hood and anexhaust ductwork of unusually large capacity.

The problems facing the inventors were manifold. The initial problem ofeffecting smoke removal from the cutting building was strongly relatedwith the necessity that the apparatus be economical to fabricate andmaintain and that it be rugged for mill service. In addition, cleaningof the apparatus should be easily accomplished and its operation andmaintenance sufficiently simple so that it could be entrusted tounskilled individuals. Solutions to these problems within therestrictive economic and structural parameters have been obtained by theinventors through a systems design wherein each major component of acutting table together with the cooperating exhaust system has beensubstantially modified to produce an interrelated apparatus functionallyand structurally different from the known prior art.

SUMMARY OF THE INVENTION In order to avoid exhausting the entire cuttingtable which was considered impractical, the inventors considered thatthe utilization of horizontal ducts under the cutting table withindividual exhausting means would both localize the exhaust capacitiesto that of just a few ducts and permit the utilization of an exhaustsystem which is practical from both an economic and space standpoint. Itwas considered that if the support for the metal being cut wassufficiently thin, photoelectric cells might be actuated by the plasmaproduced by the torch to control the exhaust flow. But this in itselfposed a problem inasmuch as it was known from experience that thesupport gratings vertical dimension had to be sufficient so that itcould be cut repeatedly and still retain the structural capability tosupport heavy loads. Still further, the grating needed to besufficiently flexible to withstand flattening by heavy loads withoutdistortion by repeated heating and cutting. These requirements inthemselves seemed inconsistent with the design of a grating which wouldpermit the plasma of a cutting torch to extend below it in all types oftorch cutting operations. Still further, the openings in the gratingshould be such as to provide support for small pieces of plate and scrapwhich may be left on the grating after completion of a cuttingoperation. Moreover, needless to say, the cost of the grating which isconsidered expendable could not be great. The inventors solution was tolocate the support bars diagonally at 45 whereby long cuts of the barswere statistically reduced when the usual rectangular type patterns arebeing cut in supported metal plates. Short stiffening bars are staggeredbetween the supporting bars so that the longer diagonal bars remainstable to the extent that they will not roll or twist under impact whileat the same time the entire assembly is sufficiently flexible for itspurposes The grating could have a greatly reduced vertical dimension fora given amount of use. Thus it was possible to provide photoelectriccells and associated circuitry for the actuation of exhaust from theducts involved. The ducts have been formed by utilizing the steel platepartitions which support grating to function as the sides of the ductsand the Work piece itself forms the top of the ducts. By making thesepartitions removable, cleaning becomes a simple task compared toconventional designs. The resulting structure is rugged and incombination with the expendable grating, the heavy plate partitionsshould last almost indefinitely. An exhaust system which is selective tothe duct space wherein the actual burning and smoke production takesplace is provided by a manifold located longitudinally adjacent theburning table and includes therein a series of openings, one of which isfor each duct. Such openings are located in a horizontal dividing platewithin the manifold and a simple hinged horizontal plate or door with adeep lip soft sealing ring provides a self-cleaning effective sealingvent door for each duct. Also an arrangement is provided whereby heavyparticles and objects are slung out of the path of the air and droppedto the bottom plate of the chamber for easy removal. The hinged door isvirtually fool proof and is of a type which can be operated over anextended period without appreciable air leakage. The long lipped sealingring eliminates the necessity of machining around the 'vent opening andalignment is therefore not critical. The arrangement also minimizesassembly time machining and thus contributes to economical fabrication.Although the air seal is not absolutely airtight, it is sufficiently sofor the function of the apparatus and does not require adjustment.

The system has proved superior in operation. Fumes and smoke areeffectively drawn away from under the metal plate being cut by theplasma torch and escape into the atmosphere of the building is minimal.The contaminates produced are carried away to a separation means andthere is little or no contamination of the atmosphere of the cuttingbuilding or outside caused by the cutting operation. The operator of theequipment no longer needs breathing apparatus and the job is no longeran unpopular one. Thus the system in accordance with the invention isrelatively easy to operate, clean and maintain, and functionseffectively.

Other objects, adaptabilities and capabilities will appear as thedescription progresses, reference being had to the accompanyingdrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the cuttingtable in accordance with the invention with a grating (which is partlybroken away to show underlying structure) in place;

FIG. 2 is a cross sectional view taken on lines IIII of FIG. 1;

FIG. 3 is a cross sectional view of the exhaust manifold whichillustrates the operation of the hinged cover plates;

FIG. 4 is a cross sectional view which shows the mounting for thephotoelectric cell;

FIG. 5 is a simplified schematic wiring diagram of the circuitry foractuating selected closures in the exhaust manifold;

FIG. 6 is a schematic diagram which shows the pneumatic system utilizedto open and close the hinged cover plates; and

FIG. 7 is an elevational view showing the relationship of the exhaustmanifold with the baghouse wherein contaminates are separated.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, it willbe seen that a horizontal base plate 10 has welded thereto at one end aside support 11 and at the other end an exhaust manifold 12. A pluralityof vertical steel strip members 14 are affixed to the inner facingsurface of side support 11 and of the exhaust manifold 12 so as todefine facing vertical grooves 15. The metal dividing plates 16 arevertically disposed and have their ends received in grooves so as toconstitute vertical sides of duct means or channels 17. The bottom ofeach channel 17 is formed by the base plate 10 which supports the plates16. The top of each channel 17 is formed by the work piece, metal plate20 upon which the cutting operation is performed and which is supportedby the grating 21. The grating 21 comprises four steel rectangularframes 22, each of which has a plurality of steel bars 24 which arewelded across frame 22 on the diagonal to form a 45 angle with the sidesof frame 22. The steel bars 24 are connected by staggered stiffeningbars 25 and the grating 21 rests on the tops of the metal plates 16between the side support 11 and the exhaust manifold 12. The four frames22 may be spot-welded together to form the assembled grating 21.However, in practice, this has not been found necessary. As assembled,the apparatus is relatively large. Thus, the base plate 10 is 2 inchesthick and presents dimensions in plan of about 37 by 22 feet. The metaldivider plates 16 rise about 18 inches vertically and measure about 16feet across horizontally. The grating 21 is approximately 4 inches indepth. The exhaust manifold 12 is approximately 3 feet in width andsomewhat over 4 feet high.

The metal plate 20 upon which the cutting operation is to take place ispreferably located with one edge adjacent to the exhaust manifold 12 toform, with the metal divider plates 16 and the base plate 10, reasonablycontinuous channels 17. A plasma cutting torch 26 is placed as desiredon the metal plate 20 and it may be guided and caused to travel eithermanually or automatically along a predetermined path by means well knownin the art. The cutting plasma 27 projects below the grating 21. Foreach channel 17 a photoelectric cell 30 is mounted on the back or outersurface of side support 11 so as to be responsive through an opening 73to radiation from the cutting flame 27. The photoelectric cell 30 isshown in and described in more detail with reference to FIG. 4. Also, aswill be described in more detail hereafter, the photoelectric cell 30when receiving radiation from cutting flame 27 causes a valve means 31to open in the manifold 12. Valve means 31 covers and thus controls anopening 32 in a horizontal dividing plate 34 which divides upper andlower chambers 35 and 36, respectively, of exhaust manifold 12. Theupper chamber 35 extends the entire length of the exhaust manifold 12whereas there is a separate lower chamber 36 communicating with eachchannel 17 through a port 37 into manifold 12. An extension 40 which isrigidly secured to the upper portion of the exhaust manifold 12pivotally carries an actuating means comprising a pneumatic cylinder 41which includes a stem 42 connected to an arm 44 which in turn is rigidlyconnected to a hatch weldment 45 which has affixed thereto the coveringplate 46 for opening 32. A circular seal ring 47 is connected by bolts33 to the covering plate 46 so as to provide a seal about the peripheryof the opening 32. Ring 47 is a known type sold by the Banbury EquipmentCorporation in connection with vacuum pads and is described in US. Pat.No. 3,183,032 to Warfel of May ll, I965. A rear access opening 50 intoupper chamber 35 is covered by a rear cover plate 51 which includes anaccess cover 52 and a bearing plate 54 disposed between the access cover52 and the rear cover plate 51. The rear cover plate 51 includes anopening 55 and the access cover 52 includes an opening 56 for stem 42. Afurther smaller opening 57 is provided in bearing plate 54 which is justlarge enough to receive the cylindrical stem 42. The hatch weldment 45is hinged about a pin 60 which is carried by bearing member 61 welded tothe horizontal dividing plate 34.

In FIG. 4, a typical photoelectric cell 30 is shown mounted on the sidesupport 11. Cell 30 is enclosed within a closure 62 which is attached tomounting bars 64 which in turn are secured to side support 11. Amounting panel 65 is affixed to closure 62 and carries a bracket 66which is secured thereto by bolts 67. The photoelectric cell receptacle70 is mounted on bracket 66 by means of a threaded nipple 71 whichpasses through an opening in bracket 66 and receives a nut 72. Anopening 73 in side support 11 receives a nipple 74 which extendsoutwardly and carries on its end a soft rubber hose member 75. Adjacentto the end of nipple 74 and maintained in position by hose member 75 isa clear glass plate 76. A nipple 74 is aligned with each channel 17 sothat light emanating therein from the cutting flame 27 is received viaglass plate 76 by cell 30. It will be understood that wiring details arenot shown in FIG. 4 inasmuch as to do so would not assist inunderstanding the invention. In FIG. 5, however, a simplified wiringdiagram for one of the photoelectric cells 30 is set forth.

As shown in FIG. 5, each cell 30 controls, through a photo relay 77,three further relays 80, 80a and 80b which in turn energize threesolenoids 81, 81a and 81b which, still further, actuate pneumatic valves82, 82a and 82b which, in turn, cause valve means 31 aligned with thecell 30 involved and the adjacent valve means to open or close. Thuswhen cell 30 responds to light radiated by the cutting flame 27, thephoto relay 77 closes and further relays 80, 80a and 80b are also causedto close and energize solenoids 81, 81a, and 81b to move pneumaticvalves 82, 82a and 82b whereby the valve means 31 aligned with thecorresponding cell 30 is caused to open and the valve means 31 on eachside thereof are also caused to open. Each of relays 80, 80a and 80b,and photo relay 77 are biased so as to be open when not energized due tolight radiation received by cell 30. Also it should be understood thatmanually controlled overrides, not shown, are preferably provided forthe photo relays 77 for each cell 30.

FIG. 6 is a schematic diagram of the pneumatic system which is utilizedto open and close the individual valve means 31. Thus air is suppliedfrom an air pressure source 83 through a stop valve 84, which isnormally open when the system is operative, through a filter 85, apressure regulator 86, and lubrication means 87. A gauge 90 is connectedto the regulator 86 to show the regulated air pressure in the system.The main pneumatic line 91 has a plurality of branches each leading to apneumatic valve such as branch 93 leading to valve 82 controlled bysolenoid 81. Pneumatic valve 82 is spring biased by a spring 92 to theposition shown in FIG. 6 whereby valve means 31 is closed. The cylinder41 thus receives air under pressure from branch 93 via pneumatic valve82 and hose 94 which connects the pneumatic valve 82 with the upperportion of the cylinder 41. Air from the bottom portion of the cylinder41 under piston 95 is bled therefrom via first hose 97, then flowcontrol valve 96 which has a built-in check valve, next line 98 andfinally through the pneumatic valve 82 to the atmosphere. However, whenpneumatic valve 82 is moved to the left (as seen in FIG. 6) by actuationof solenoid 81, branch 93 is aligned through pneumatic valve 82 with theline 98 whereby air under pressure flows through flow control valve 96and hose 97 into the lower portion of cylinder 41 to cause piston 95 together with stem 42 to move to the left (as seen in FIG. 6) and open thevalve means 31. Air in the upper portion of cylinder 41 is bled to theatmosphere via hose 94 and pneumatic valve 82. It will be appreciatedthat in the apparatus disclosed there are 12 channels l7, l2photoelectric cells 30, and 12 valve means 31 each with the associatedelectrical and pneumatic actuated circuits. And also it should beunderstood that whereas each photoelectric cell actuates not only itscorresponding valve means 31 but also the valve means 31 adjacentthereto on either side, this does not apply to the valve means at thefar ends where only the inboard adjacent valve means is actuated by theoutboard photoelectric cells 30.

As may be seen in FIG. 7, a bag house 100 which includes air perviousbags and fan means, is located outside the finishing building 101 andreceives exhaust from the upper chamber 35 of the exhaust manifold 12through an exhaust duct 102 which extends through an opening in the wallof finishing building 101. Means for separating contaminents as may beutilized in bag house 100 are conventional and generally widely known inthe field to which the invention pertains. Therefore, a description oftheir exact nature and type is not necessary for an understanding anduse of the invention by a person skilled in the art.

In operation, a work piece comprising metal plate 20 which is to be cutby a plasma arc torch 26 is placed on the grating 21 and a pattern islaid out for the plasma cutting torch 26 to follow. The cutting is thencommenced and the cutting flame 27 which extends below grating 21immediately causes cell 30 in the same channel 17 to open up thecorresponding valve means 31 and the valve means 31 on either sideadjacent thereto. Smoke is initially generated or produced by thecutting torch 26 under plate 20 and it is immediately drawn throughchannel 17 and via port 37 into the lower chamber 36 of exhaust manifold12. There it makes an abrupt turn upward so that heavy air borneparticles are flung to the bottom of the chamber 36 and the smoketravels through the opening 32 into the upper chamber 35 of exhaustmanifold 12. Smoke is carried through such chamber 35 into the exhaustduct 102 and finally into the bag house by exhaust means such as exhaustfans which are included in the bag house 100. At this location, thecontaminents are separated from the exhaust gases and the air leavingthe bag house is substantially uncontaminated. As the cutting torch 26moves along its predetermined pattern whereby the cutting flame 27travels from one channel 17 to the adjacent channel 17 a differentphotoelectric cell 30 is actuated so that at all times the channels 17being exhausted are only those in which the flame 27 is received andthose on either side of the channel receiving the cutting flame 27. Thisnot only makes the cutting table more efficient inasmuch as there is noperiod of time in which a cutting flame 27 is over a channel not beingexhausted, but also it precludes a build-up of smoke in the adjacentchannel 17. As the-cutting torch 26 moves along a metal plate 20 it alsotends to cut the steel bars 24 although if the torch is properly set, itwill not cut them entirely but rather tends to cut notches in them. As apractical matter, it is highly unlikely that the torch 26 will travelparallel to the steel bars 24 for any substantial distance.

When any given valve means 31 is no longer actuated in an open positionby a cell 30, it closes, and due to the weight of the plate 46 and forceexerted by air cylinder 41 its disposition on the partition plate 34with resilient lip members 47 is such that leakage of air through theopening 32 is minimal.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. An expendable grating for a burning table generally utilized for longstraight cuts in substantially one direction and other straight cuts ina direction substantially at right angles to said one direction, whichcomprises a plurality of bars each disposed at a bias to each of saiddirections, said plurality of bars connected to each other by furtherbars which are also at a bias to said directions.

2. An expendable grating in accordance with claim 1 wherein said furtherbars are substantially at right angles to said first mentioned bars.

3. An expendable grating in accordance with claim 2 wherein said firstmentioned bars each run diagonally across a width of the table and saidfurther bars comprise short stiffening bars connecting adjacent of saidfirst mentioned bars.

4. An expendable grating in accordance with claim 1 in combination withsupporting means comprising a plurality of vertically disposed metalpartitions.

5. An expendable grating in accordance with claim 1 in combination witha cutting torch, the depth of said grating being shallow relative to theoperative length of the flame of said cutting torch whereby when saidtorch is cutting a plate supported by said grating, said flame extendsbelow said grating.

6. An expendable grating in accordance with claim wherein said firstmentioned bias is at an angle of about 45 to said directions.

7. An expendable work support member for a table for cutting steel plateor the like by a cutting torch, said support comprising a horizontallydisposed rectangular steel frame, a plurality of steel bars extendingdiagonally across said frame for receiving said steel plate or the like,and a plurality offurther shorter stiffening bars extending between andrigidly connecting adjacent of said first mentioned bars.

8. An expendable work support member in accordance with claim 7 whereinsaid frame has a longer length than width, said first mentioned barsbeing rigidly connected to said frame and extending diagonally acrossthe width of said frames.

9. An expendable work support member for a table which supports steelplate or the like while it is cut by a cutting torch, said supportmember comprising a horizontally disposed steel frame, a plurality ofsteel load bearing bars extending diagonally across said frame forreceiving said steel plate or the like, and a plurality of furthershorter stiffening steel bars connecting said first mentioned bars, saidfurther bars connecting at least two of said first mentioned barsstaggered relative to the further bars connecting at least two other ofsaid first mentioned bars.

10. An expendable work support member in accordance with claim 9 whereinsaid further bars are at right angles to said first mentioned bars.

11. An expendable work support member in accordance with claim 9 whereinsaid frame is rectangular in configuration as seen from above.

12. An expendable work support member in accordance with claim 11wherein said first mentioned bars are disposed at an angle of about 45relative to said frame.

13. An expendable work support member in accordance with claim 12wherein said further bars are at right angles to said first mentionedbars.

14. An expendable grating for supporting a metal plate during a cuttingoperation which comprises a steel rectangular frame, a plurality ofsteel bars for bearing said metal plate welded across said frame to forman angle of about 45 with the sides of said frame, said steel bars beingconnected by staggered stiffening bars.

1. An expendable grating for a burning table generally utilized for longstraight cuts in substantially one direction and other straight cuts ina direction substantially at right angles to said one direction, whichcomprises a plurality of bars each disposed at a bias to each of saiddirections, said plurality of bars connected to each other by furtherbars which are also at a bias to said directions.
 2. An expendablegrating in accordance with claim 1 wherein said further bars aresubstantially at right angles to said first mentioned bars.
 3. Anexpendable grating in accordance with claim 2 wherein said firstmentioned bars each run diagonally across a width of the table and saidfurther bars comprise short stiffening bars connecting adjacent of saidfirst mentioned bars.
 4. An expendable grating in accordance with claim1 in combination with supporting means comprising a plurality ofvertically disposed metal partitions.
 5. An expendable grating inaccordance with claim 1 in combination with a cutting torch, the depthof said grating being shallow relative to the operative length of theflame of said cutting torch whereby when said torch is cutting a platesupported by said grating, said flame extends below said grating.
 6. Anexpendable grating in accordance with claim 1 wherein said firstmentioned bias is at an angle of about 45* to said directions.
 7. Anexpendable work support member for a table for cutting steel plate orthe like by a cutting torch, said support comprising a horizontallydisposed rectangular steel frame, a plurality of steel bars extendingdiagonally across said frame for receiving said steel plate or the like,and a plurality of further shorter stiffening bars extending between andrigidly connecting adjacent of said first mentioned bars.
 8. Anexpendable work support member in accordance with claim 7 wherein saidframe has a longer length than width, said first mentioned bars beingrigidly connected to said frame and extending diagonally Across thewidth of said frames.
 9. An expendable work support member for a tablewhich supports steel plate or the like while it is cut by a cuttingtorch, said support member comprising a horizontally disposed steelframe, a plurality of steel load bearing bars extending diagonallyacross said frame for receiving said steel plate or the like, and aplurality of further shorter stiffening steel bars connecting said firstmentioned bars, said further bars connecting at least two of said firstmentioned bars staggered relative to the further bars connecting atleast two other of said first mentioned bars.
 10. An expendable worksupport member in accordance with claim 9 wherein said further bars areat right angles to said first mentioned bars.
 11. An expendable worksupport member in accordance with claim 9 wherein said frame isrectangular in configuration as seen from above.
 12. An expendable worksupport member in accordance with claim 11 wherein said first mentionedbars are disposed at an angle of about 45* relative to said frame. 13.An expendable work support member in accordance with claim 12 whereinsaid further bars are at right angles to said first mentioned bars. 14.An expendable grating for supporting a metal plate during a cuttingoperation which comprises a steel rectangular frame, a plurality ofsteel bars for bearing said metal plate welded across said frame to forman angle of about 45* with the sides of said frame, said steel barsbeing connected by staggered stiffening bars.